5th lecture - hypnotics & sedatives Flashcards
define neuroleptic
(of a drug) tending to reduce nervous tension by depressing nerve functions; are both tranquillizers & antipschyotics.
function of the Cerebral cortex
consciousness, memory, thought (cortical functions)
function of the brain Centres in the subcortical regions
emotions, moods, experiences/perception (subcortical functions)
psychosedative effect =
Depression of cortical brain function
psychostimulation =
Stimulation of cortical brain function
euphoric, psychostimulatory drugs have what type of effects
Psychological stimulation
Neurosis means
a neurotic disorder, irritability or other such effects resulting from psychological overload.
involves symptoms of stress (depression, anxiety, obsessive behaviour, hypochondria) but not a radical loss of touch with reality.
In veterinary medicine neuroleptics and tranquilizers are described as one group of drugs, called:
major tranquilizers.
antipsychotics/anti-hallucinogenics are also known as
neuroleptics
overall depressant effect on the CNS
some subgroups of neuroleptics include: (4)
Phenothiazines (e.g. Plegicil/ace)
Thioxanthenes
Butyrophenones
Indoles (e.g. ondis and tadalafil)
Example of a common phenothiazine used in vet med
acepromazine (Plegicil)
example of a butyrophenone
(neuroleptic subgroup)
azaperone is used in vet med
example of an indole
(neuroleptic subgroup)
reserpine
neuroleptics pharmacokinetics (3)
Absorption is good,
they penetrate the blood-brain barrier, metabolism occurs in the liver.
neuroleptics mechniams of action
They suppress all mediatory systems in the brain and in the periphery:
adrenergic,
cholinergic,
histaminergic ,
serotonergic,
and dopaminoreactive systems.
The main effect and also secondary effects of neuroleptics are primarily related to the
dopamine blocking effect as the dopaminergic transmission in the central nervous system is blocked.
pathway from Tyrosine to Noradrenaline
Tyrosine, L-DOPA, Dopamine, Noradrenaline
Dopamine is a mediator with a catecholamine structure, mainly functioning in the brain structures related to
regulation of the psyche/ psychological domain: striatum, hypothalamus, hippocampus, mesolimbic structures and the fourth ventricle.
name dopamine receptors
5 subtypes are distinguished.
Pharmacologically important D1, D2 and D3.
The effect of neuroleptics is realised through D2 receptors.
Dopamine is broken down by
MAO and COMT.
monoamine oxidase
catechol O methyltransferase
neuroleptic antipshyotic effect is due to the blocking of what?
Antipsychotic effect due to dopamine blocking effect, limbic and cortical dopaminergic transmissions are blocked.
neuroleptic sedative effect is due to the blocking of what?
Sedative due to cholino and histamine blocking effect.
Cardiovascular effects of neuroleptics
Blockade of the central and peripheral effects of catecholamines:
Alfa-blockade = eripheral vasodilation
Arterial hypotension, even up to shocklike conditions especially in compromised patients.
define intrathecal
introduced into or occurring in the space under the arachnoid membrane of the brain or spinal cord.
Respiratory effects of neuroleptics
Clinical doses have little effect upon respiratory activity.
Respiratory rate is often depressed, but minute volume remains normal.
Respiratory depression may be exaggerated when phenothiazines are administered with other CNS respiratory depressants (opioids, isoflurane) or in high doses.
Musculosceletal effects of neuroleptics
Phenothiazines provide good muscle relaxation and are often used in conjunction with anesthetics that do not provide muscle relaxation or that result in muscle rigidity
(e.g. ketamine).
neuroleptics and Thermoregulation (2)
Phenothiazines alter thermoregulation by decreased catecholamine binding in the hypothalamus (where thermoregulation is controlled centrally),
as well as by altering vasomotor tone in the peripheral vessels that participate in heat retention and elimination.
neuroleptics’ effect on blood (2)
Acepromazine has been shown to decrease platelet aggregation – should be used with caution in patients with any coagulopathy or thrombocytopenia.
Phenothiazines markedly reduce the hematocrit of animals. They cause splenic sequestration of red blood cells and markedly reduce the hematocrit level.
neuroleptics’ Interactions with other medicinal products.
NL increase the potency of hypnotics without causing any sleepiness effect by themselves.
They potentiate the effect of general anaesthetics.
They increase the potency of analgesics without having any analgesic effect by themselves.
They potentiate the effect of muscle relaxants.
neuroleptics Should be used cautiously with any drugs that also produce
vasodilation or hypotension.
e.g. beta blockers
neuroleptic contraindications
Phenothiazines should not be used in patients that are dehydrated, hypovolemic, bleeding, or in shock (vasodilation).
Not in patients with coagulopathies or thrombocytopenia.
Use cautiously in boxer dogs, brachiocephalic dogs, breeding stallions and debilitated animals.